In general, a heat sink member employing molybdenum (Mo) is known as a heat sink member for absorbing heat generated from an electronic component or the like and radiating the same outward. A Cu/Mo/Cu clad member prepared by employing molybdenum as a substrate and cladding the same with Cu as ply members is known as this heat sink member employing molybdenum. In general, this Cu/Mo/Cu clad member is manufactured by hot pressure welding or cold pressure welding (cold rolling). However, Mo as the substrate is so hard and small in elongation that the same is easily cracked or chapped in the hot pressure welding or the cold pressure welding (cold rolling). Particularly in the method cold-pressure-welding (cold-rolling) the Cu/Mo/Cu clad member, there is such inconvenience that the substrate consisting of Mo is easily cracked or chapped when rolling the substrate consisting of Mo and the ply members consisting of Cu and bonding the same to each other.
In general, therefore, a heat sink member inhibiting a substrate consisting of Mo (molybdenum) from development of cracks and chaps by bonding the substrate consisting of Mo and ply members consisting of Cu to each other with brazing filler metal in place of the hot pressure welding or the cold pressure welding (cold rolling) is proposed. Such a heat sink member is disclosed in Japanese Patent Laying-Open No. 11-284111, for example.
A heat sink member consisting of a Cu/Mo/Cu clad member prepared by bonding ply members consisting of plates of copper (Cu) and a substrate consisting of a plate of molybdenum (Mo) to each other with brazing filler metal consisting of an Mn—Ni—Cu alloy is disclosed in the aforementioned Japanese Patent Laying-Open No. 11-284111. In this bonding method employing the brazing filler metal consisting of the Mn—Ni—Cu alloy disclosed in Japanese Patent Laying-Open No. 11-28411, the substrate consisting of the plate of Mo (molybdenum) is not pressure-welded in manufacturing of the heat sink member consisting of the Cu/Mo/Cu clad member, whereby it is possible to inhibit the substrate consisting of the plate of molybdenum from development of cracks and chaps.
In the method bonding the substrate consisting of Mo and the ply members consisting of Cu to each other with the brazing filler metal consisting of the Mn—Ni—Cu alloy disclosed in the aforementioned Japanese Patent Laying-Open No. 11-28411, however, there is such inconvenience that the thermal expansion coefficient of the Cu/Mo/Cu clad member enlarges due to the brazing filler metal. When arranging a semiconductor element consisting of silicon or the like having a small thermal expansion coefficient on the heat sink member consisting of the Cu/Mo/Cu clad member, therefore, thermal expansion coefficient difference between the heat sink member and the semiconductor element enlarges. Consequently, there is such a problem that cracks or chaps easily develop on the junction between the semiconductor element and the heat sink member consisting of the Cu/Mo/Cu clad member. When employing the brazing filler metal consisting of the Mn—Ni—Cu alloy as in the aforementioned Japanese Patent Laying-Open No. 11-284111, there is also such inconvenience that thermal conductivity of the heat sink member consisting of the Cu/Mo/Cu clad member remarkably lowers. Thus, there is also such a problem that heat radiability of the heat sink member remarkably lowers.